Ashwagandha Raised Testosterone by 15 Percent in Overweight Men Over 40 and Did Nothing for How They Felt. The Trials Behind the Most Popular Herb in Men's Health, and the Liver Cases That Got It Banned in Denmark.
Ashwagandha sits in a different category from most ingredients in a testosterone booster. D-aspartic acid rests on one positive trial. Tribulus has none. Ashwagandha root extract has at least four randomized, placebo-controlled trials in men that measured testosterone, and three of them found it went up. That is enough evidence to take seriously and little enough that the details matter more than the headline. The trials are small, they used three different proprietary extracts at different withanolide concentrations, the men ranged from untrained 20-year-olds to overweight 65-year-olds, and the one trial designed to ask whether men actually felt any better found they did not. This article walks through each trial, the cortisol data that probably explain the testosterone signal, the semen findings, the strength results, and the liver and thyroid reports that have made European regulators uneasy.
Key Takeaways: What the Ashwagandha Evidence Actually Shows
Ashwagandha root extract raised testosterone relative to placebo in three of four randomized controlled trials that measured it in men. Wankhede and colleagues in 2015 gave 57 untrained men aged 18 to 50 a 300 mg dose of KSM-66 extract twice a day for eight weeks alongside a resistance programme, and reported a testosterone rise of 96.2 ng/dL against 18.0 ng/dL on placebo. Lopresti, Drummond and Smith in 2019 ran a 16-week crossover trial in 43 overweight men aged 40 to 70 with mild fatigue and found testosterone 14.7 percent and DHEA-S 18 percent higher on Shoden extract than on placebo, with no difference in fatigue, vitality or sexual well-being scores. Gupta and colleagues in 2013 gave 46 men with low sperm counts 675 mg a day of root extract for 90 days and reported testosterone up 17 percent, luteinizing hormone up 34 percent and sperm concentration up 167 percent against placebo. Ziegenfuss and colleagues in 2018 gave 38 recreationally active men 500 mg a day of Sensoril extract for 12 weeks and found larger squat and bench press gains than placebo but no change in testosterone. The most consistent finding across the literature is a fall in cortisol, 27.9 percent against 7.9 percent on placebo in the 64-person Chandrasekhar trial of 2012, which is the most likely route by which a testosterone effect occurs. A 2020 case series in Liver International described five patients in Iceland and the United States with jaundice after two to twelve weeks of ashwagandha at 450 to 1,350 mg a day, all of whom recovered within five months. Denmark prohibited ashwagandha in food supplements after a 2020 risk assessment concluded it could affect thyroid and sex hormones. Nothing in the human literature runs longer than 16 weeks.
Four Placebo-Controlled Trials, 184 Men, Three Positive Results
Number of men randomized in each double-blind, placebo-controlled trial of standardized ashwagandha root extract that measured testosterone, coloured green where testosterone rose relative to placebo and grey where it did not. Gupta and colleagues in 2013 reported a 17 percent rise in 46 oligospermic men on 675 mg a day of root extract for 90 days. Wankhede and colleagues in 2015 reported a rise of 96.2 ng/dL against 18.0 ng/dL on placebo in 57 untrained men on 600 mg a day of KSM-66 over eight weeks of resistance training. Ziegenfuss and colleagues in 2018 found no difference in 38 recreationally active men on 500 mg a day of Sensoril over 12 weeks of training. Lopresti, Drummond and Smith in 2019 reported testosterone 14.7 percent higher than placebo in a crossover trial of overweight men aged 40 to 70 on Shoden delivering 21 mg of withanolide glycosides a day, with 43 completing. The 2010 series by Ahmad and colleagues in 75 infertile men is not shown because it had no placebo group. Three of the four trials were funded or supplied by the manufacturer of the extract tested.
What is ashwagandha and why would it affect testosterone?
Ashwagandha is the dried root of Withania somnifera, a small shrub in the nightshade family, and the reason it might change testosterone is that its active compounds appear to lower cortisol, and cortisol suppresses the hormone axis that drives testosterone production. The root contains a family of steroidal lactones called withanolides, and commercial extracts are standardized to a withanolide percentage: KSM-66 at about 5 percent, Sensoril at about 10 percent, Shoden at about 35 percent. In animal work, withanolides reduce corticosterone output and dampen the hypothalamic-pituitary-adrenal response to stress. In men, the biological logic runs as follows. Chronically elevated cortisol reduces the pulsatile release of gonadotropin-releasing hormone from the hypothalamus, lowers luteinizing hormone from the pituitary and blunts the Leydig cell response to whatever luteinizing hormone does arrive. Lower cortisol should, in principle, lift that brake. A second proposed route is antioxidant activity within the testis, where withanolides reduce lipid peroxidation in seminal plasma in the infertility studies. Neither mechanism has been shown directly in a human trial to be the cause of the testosterone changes reported. What has been shown is that the cortisol effect is real and fairly repeatable, and that the testosterone effect appears mainly in populations where a stress or metabolic brake on the axis is plausible: untrained men starting a hard programme, overweight men in their fifties and sixties, and men attending a fertility clinic.
Which randomized trials measured testosterone in men taking ashwagandha?
Four randomized, double-blind, placebo-controlled trials have measured testosterone in men taking a standardized ashwagandha root extract, with a combined enrolment of about 184 men, and one uncontrolled series in 75 infertile men reported the hormone as well. In order of publication: Gupta and colleagues in Reproductive BioMedicine Online in 2013 enrolled 46 oligospermic men aged 22 to 40 and gave 25 of them 675 mg a day of root extract in three divided doses for 90 days. Wankhede, Langade and colleagues in the Journal of the International Society of Sports Nutrition in 2015 enrolled 57 men aged 18 to 50 with little resistance-training experience and gave them 300 mg of KSM-66 twice a day for eight weeks while both groups trained. Ziegenfuss and colleagues in Nutrients in 2018 enrolled 38 recreationally active men and gave them 500 mg a day of Sensoril, a water-based extract, for 12 weeks of supervised training. Lopresti, Drummond and Smith in the American Journal of Men's Health in 2019 enrolled overweight men aged 40 to 70 with self-reported mild fatigue and ran a crossover design, eight weeks on 21 mg a day of withanolide glycosides delivered as Shoden and eight weeks on placebo, with 43 men completing. The earlier series by Ahmad and colleagues in Fertility and Sterility in 2010 gave 75 infertile men 5 grams a day of raw root powder for three months with no placebo arm. Every one of these trials was small. The largest arm in any of them was 29 men. Three of the four controlled trials were funded or supplied by the company that makes the extract tested, which is normal in this field and is a reason to weight the pattern across trials more than any single number.
What did the 2015 trial in men starting a lifting programme find?
The Wankhede trial found that untrained men who took 600 mg a day of KSM-66 while following an eight-week resistance programme gained more testosterone, more strength and more muscle than men on placebo following the same programme. Fifty-seven men aged 18 to 50 were randomized, and 50 completed. Total testosterone rose by 96.2 ng/dL in the ashwagandha group against 18.0 ng/dL in the placebo group, a difference the authors reported as significant. Bench press one-repetition maximum rose by 46.0 kg in the ashwagandha group against 26.4 kg on placebo. Leg extension rose 14.5 kg against 9.8 kg. Arm muscle cross-section increased 8.6 square centimetres against 5.3, and chest circumference 3.3 centimetres against 1.4. Body fat fell 3.5 percent against 1.5 percent. Serum creatine kinase, a marker of muscle damage, was lower after exercise in the supplemented men, which the authors read as faster recovery. These are large effects for a herb, and two features of the design help explain them. The men were beginners, so the training itself was driving rapid adaptation and a modulator of stress and recovery had a lot of room to work. And the trial ran for only eight weeks, the window in which novice strength gains are steepest. The 96 ng/dL testosterone rise is roughly 3.3 nmol/L, about what a man might see from losing 10 to 15 percent of his body weight if he started obese. Whether that persists past eight weeks is not something the trial can answer, and no follow-up has repeated it in trained men with KSM-66.
What did the 2019 trial in overweight men aged 40 to 70 find?
The Lopresti trial found that ashwagandha raised testosterone by 14.7 percent and DHEA-S by 18 percent relative to placebo over eight weeks in overweight men aged 40 to 70, and that the men could not tell the difference. This is the most relevant trial for a man over 40 because it is the only one that enrolled that age group and the only one that measured how participants felt as a primary outcome. Overweight men with mild fatigue were randomized to eight weeks on Shoden, standardized to deliver 21 mg of withanolide glycosides a day, followed by eight weeks on placebo, or the reverse order, with 43 men completing both periods. The hormone results were clear: DHEA-S rose 18 percent more on ashwagandha than on placebo, and total testosterone rose 14.7 percent more. Cortisol and estradiol did not change significantly. The symptom results were equally clear in the opposite direction. Scores on the Aging Males' Symptoms questionnaire, the fatigue scale of the Profile of Mood States and a sexual well-being measure improved in both periods and did not differ between ashwagandha and placebo. The authors were direct about this: the hormonal changes were not accompanied by changes in how men felt or functioned. That gap is the single most useful finding in the ashwagandha literature. A 15 percent rise in testosterone within the normal range, in a man who starts around 15 nmol/L, moves him to about 17 nmol/L. That is a real biochemical change and a small one, and the trial suggests it is below the threshold at which a man notices anything. It also means that the questionnaire improvements men report on ashwagandha in open-label settings are probably placebo, which the crossover design in this trial was well placed to expose.
The Hormones Moved. The Men Did Not Notice.
Percent difference between ashwagandha and placebo after eight weeks in the Lopresti 2019 crossover trial of overweight men aged 40 to 70 with mild fatigue, published in the American Journal of Men's Health. DHEA-S was 18 percent higher and total testosterone 14.7 percent higher on Shoden extract than on placebo. Cortisol and estradiol did not differ significantly and are plotted at zero. Scores on the fatigue scale of the Profile of Mood States, the Aging Males' Symptoms questionnaire and a sexual well-being measure improved during both the ashwagandha and placebo periods and did not differ between them, so they are also plotted at zero. This is the only ashwagandha trial to enrol men over 40 and the only one to make how men felt a primary outcome. A 14.7 percent rise inside the normal range, for example from 15 to about 17 nmol/L, is a real biochemical change and appears to sit below the threshold at which men perceive a difference in energy, mood or libido.
Does ashwagandha lower cortisol, and does that explain the testosterone effect?
Yes, lower cortisol is the most repeatable finding in the ashwagandha trials, and it is the most plausible explanation for the testosterone signal, though no trial has demonstrated the link directly. The clearest cortisol result comes from Chandrasekhar, Kapoor and Anishetty, published in the Indian Journal of Psychological Medicine in 2012. Sixty-four adults with a history of chronic stress took 300 mg of KSM-66 twice a day or placebo for 60 days. Serum cortisol fell 27.9 percent in the ashwagandha group against 7.9 percent on placebo. Scores on the Perceived Stress Scale fell 44 percent against 5.5 percent. Later trials using different extracts and doses, including a 2019 trial by Lopresti and colleagues at 240 mg a day of Shoden over 60 days in 60 stressed adults, reported morning cortisol reductions in the same direction, and a 2021 dose-ranging trial by Salve and colleagues found reductions at both 250 and 600 mg a day. Cortisol suppresses the reproductive axis at the hypothalamus, the pituitary and the testis, so a compound that lowers cortisol should modestly raise testosterone in men whose cortisol was elevated to begin with. That prediction fits the pattern in the trials. The populations that showed a testosterone rise were untrained men under a new physical stress, overweight men in mid-life and infertile men under psychological stress. The population that did not, recreationally active men in the Ziegenfuss trial, had less reason to have a cortisol brake in place. It also predicts that ashwagandha will do little for a man whose testosterone is low because his testes are failing or because his pituitary is not signalling, and nothing in the literature contradicts that.
The Most Repeatable Effect Is on Cortisol
Percent fall from baseline in serum cortisol and in Perceived Stress Scale score over 60 days in the Chandrasekhar, Kapoor and Anishetty trial, published in the Indian Journal of Psychological Medicine in 2012. Sixty-four adults with a history of chronic stress took 300 mg of KSM-66 twice a day or placebo. Cortisol fell 27.9 percent on ashwagandha against 7.9 percent on placebo, and perceived stress fell 44 percent against 5.5 percent. Later trials with Shoden at 240 mg a day and with KSM-66 at 250 and 600 mg a day reported reductions in the same direction. Cortisol suppresses the reproductive axis at the hypothalamus, pituitary and testis, so a cortisol-lowering agent should modestly raise testosterone in men whose cortisol was elevated, which fits the pattern that the positive testosterone trials enrolled untrained men under new training stress, overweight men in mid-life and infertile men, while the null trial enrolled recreationally active men.
- KSM-66, 600 mg/day
- Placebo
Does ashwagandha improve sperm quality or male fertility?
One placebo-controlled trial and one uncontrolled series both reported improvements in semen parameters, and the controlled trial reported changes large enough that they deserve replication before being trusted. Gupta and colleagues in 2013 randomized 46 men with sperm concentrations below 20 million per millilitre to 675 mg a day of root extract or placebo for 90 days. In the treated men, sperm concentration rose 167 percent, semen volume 53 percent, sperm motility 57 percent, serum testosterone 17 percent and luteinizing hormone 34 percent, with minimal changes on placebo. A 167 percent rise in sperm concentration from a pill is unusual. It is larger than the effect of clomiphene, an actual fertility drug, in most of its trials. Three years earlier, Ahmad and colleagues had given 75 infertile men 5 grams a day of raw root powder for three months and reported testosterone increases of roughly 10 to 22 percent across subgroups, higher luteinizing hormone, lower follicle-stimulating hormone and prolactin, and reduced oxidative stress markers in seminal plasma, but there was no placebo group and semen parameters vary widely within the same man from month to month. Both studies came from Indian centres with an interest in traditional medicine, both are small, and neither has been repeated by an independent group. The honest summary is that ashwagandha may improve sperm parameters in men with low counts, that the one controlled trial is strongly positive, and that a single 46-man trial is not a basis for a fertility decision. A man with a low sperm count should have the standard workup first.
A Fertility Result Larger Than Most Fertility Drugs
Percent change from baseline in the treated arm of the Gupta and colleagues trial, published in Reproductive BioMedicine Online in 2013. Forty-six men aged 22 to 40 with sperm concentrations below 20 million per millilitre were randomized to 675 mg a day of ashwagandha root extract in three divided doses or placebo for 90 days. In the 25 treated men, sperm concentration rose 167 percent, motility 57 percent, semen volume 53 percent, luteinizing hormone 34 percent and serum testosterone 17 percent, with minimal change on placebo. A 167 percent rise in sperm concentration exceeds what clomiphene produces in most of its trials. The study is small, from a single centre and has not been independently replicated, and semen parameters vary widely within the same man from month to month. The 2010 uncontrolled series by Ahmad and colleagues in 75 infertile men on 5 grams a day of raw root powder reported changes in the same direction. A man with a low sperm count should complete the standard fertility workup before treating this as an option.
Does ashwagandha make men stronger?
Both trials that tested ashwagandha alongside a supervised resistance programme found larger strength gains than placebo, and they disagreed about whether testosterone had anything to do with it. Wankhede in 2015 reported bench press gains of 46.0 kg against 26.4 kg and leg extension gains of 14.5 kg against 9.8 kg in untrained men over eight weeks on 600 mg of KSM-66, alongside the testosterone rise described above. Ziegenfuss and colleagues in 2018 ran the STAR trial in 38 recreationally active men over 12 weeks on 500 mg a day of Sensoril. Squat one-repetition maximum improved by about 19 kg against 10 kg on placebo, bench press by about 13 kg against 8 kg, and a 7.5 km time trial improved more in the supplemented men. Testosterone did not differ between groups at any point. The Ziegenfuss result matters because it separates the strength effect from the hormone effect. If ashwagandha helps training adaptation, the route is more likely faster recovery, lower cortisol and better sleep than a direct anabolic signal, and the lower post-exercise creatine kinase in the Wankhede trial points the same way. The strength effects in both trials are larger than would be expected from a herb, and both were in men with limited training history and short study windows, so the realistic expectation for an experienced lifter is smaller. A 2020 meta-analysis by Pérez-Gómez and colleagues of five trials found a pooled improvement in VO2max of about 3 mL per kg per minute, which is consistent with a recovery or stress effect rather than a muscle-building one.
Stronger in Both Trials. More Testosterone in Only One.
Gain in one-repetition maximum, in kilograms, with ashwagandha versus placebo in the two randomized trials that paired the extract with a supervised resistance programme. Wankhede and colleagues in 2015 gave untrained men aged 18 to 50 600 mg a day of KSM-66 for eight weeks and reported bench press gains of 46.0 kg against 26.4 kg and leg extension gains of 14.5 kg against 9.8 kg, alongside a testosterone rise of 96.2 ng/dL against 18.0 ng/dL. Ziegenfuss and colleagues in 2018 gave 38 recreationally active men 500 mg a day of Sensoril for 12 weeks in the STAR trial and reported squat gains of about 19 kg against 10 kg and bench press gains of about 13 kg against 8 kg, with no difference in testosterone at any point. The strength effect therefore does not depend on the hormone effect, and the lower post-exercise creatine kinase in the Wankhede trial points to faster recovery as the more likely route. Both trials enrolled men with limited training history over short windows, and gains for experienced lifters would be expected to be smaller.
- Ashwagandha
- Placebo
Is ashwagandha safe to take?
In the randomized trials, at 240 to 1,250 mg a day of extract for up to 16 weeks, ashwagandha produced no serious adverse events and no meaningful changes in liver or kidney markers, but a case series of liver injury, a thyroid effect and a regulatory ban in Denmark mean the safety picture is less settled than for most herbs. Björnsson and colleagues published a case series in Liver International in 2020 describing five patients, three in Iceland and two from the United States Drug-Induced Liver Injury Network, who developed jaundice and itching two to twelve weeks after starting ashwagandha at 450 to 1,350 mg a day. The injury pattern was cholestatic or mixed, liver biopsy in some cases showed the picture typical of drug-induced injury, and all five recovered within one to five months after stopping. Further cases have been reported since, and ashwagandha now appears in the LiverTox database. The absolute rate is unknown and is probably low given the volume sold, but the reaction appears idiosyncratic, meaning it is not dose-dependent and cannot be predicted from a blood test. Ashwagandha also raises thyroid hormone. Sharma and colleagues in 2018 gave 50 adults with subclinical hypothyroidism 600 mg a day for eight weeks and found thyroid-stimulating hormone fell while T4 rose 19.6 percent and T3 rose 41.5 percent, and there are case reports of thyrotoxicosis in people with normal thyroids. In 2020 the National Food Institute at the Technical University of Denmark published a risk assessment concluding that ashwagandha could affect thyroid and sex hormones and might be harmful in pregnancy, and the Danish Veterinary and Food Administration subsequently prohibited it in food supplements. Other Nordic regulators have raised similar concerns. For a man over 40 who is not on thyroid medication, has normal liver function and is not taking sedatives, the trial data suggest short-term use is well tolerated. Anyone who develops dark urine, pale stools, itching or yellowing of the eyes on ashwagandha should stop and get liver tests the same week.
How should a man over 40 use this evidence?
Treat ashwagandha as a mild cortisol-lowering agent with a modest and probably indirect effect on testosterone, expect no change in how you feel from the hormone shift alone, and give it a time-limited trial only if stress or sleep is a plausible brake on your own hormone axis. The trial that most resembles a man over 40 found testosterone 14.7 percent higher on ashwagandha than on placebo, and found the men no less fatigued, no more energetic and no better in sexual well-being than on placebo. A 15 percent lift inside the normal range does not reverse low testosterone. A man measuring 9 nmol/L will still be at roughly 10.3 nmol/L, still below the threshold at which most guidelines consider treatment, and he needs a diagnosis, not a herb. What ashwagandha can reasonably be expected to do is trim cortisol by a quarter or so in someone who is chronically stressed, help sleep in some people, and perhaps improve recovery from training. Those are worth having and are the effects to judge it by. If a man decides to try it, the doses with trial support are 600 mg a day of a 5 percent withanolide extract or 240 mg a day of a 35 percent extract, for eight to twelve weeks, with a testosterone measurement before and after if the hormone is the reason he is taking it. Longer than 16 weeks is uncharted. It should be skipped by anyone on thyroid hormone, anyone with a history of liver disease and anyone taking sedatives, and stopped at the first sign of jaundice. The strongest levers on testosterone in a man over 40 remain the ones with randomized support at scale: weight loss if overweight, seven hours of sleep, treatment of sleep apnea, resistance training and less alcohol. Ashwagandha belongs a long way below those, and above most of what shares the shelf with it.
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